Heart valve regurgitation, or leakage from the outflow to the inflow side of a heart valve, is a common occurrence in patients with heart failure and a source of morbidity and mortality in these patients. Usually regurgitation will occur in the mitral valve, located between the left atrium and left ventricle, or in the tricuspid valve, located between the right atrium and right ventricle. Mitral regurgitation in patients with heart failure is caused by changes in the geometric configurations of the left ventricle, papillary muscles and mitral annulus. Similarly, tricuspid regurgitation is caused by changes in the geometric configurations of the right ventricle, papillary muscles and tricuspid annulus. These geometric alterations result in mitral and tricuspid leaflet tethering and incomplete coaptation in systole.
Heart valve repair is the procedure of choice to correct heart regurgitation of all etiologies. With the use of current surgical techniques, between 40% and 60% of regurgitant heart valves can be repaired, depending on the surgeon's experience and the anatomic conditions. The advantages of heart valve repair over heart valve replacement are well documented. These advantages include better preservation of cardiac function and reduced risk of anticoagulant-related hemorrhage, thromboembolism and endocarditis.
Recently, several developments in minimally invasive techniques for repairing heart valves without surgery have been introduced. Some of these techniques involve introducing systems for remodeling the mitral annulus through the coronary sinus.
The coronary sinus is a blood vessel commencing at the coronary ostium in the right atrium and passing through the atrioventricular groove in close proximity to the posterior, lateral and medial aspects of the mitral annulus. Because of its position adjacent to the mitral annulus, the coronary sinus provides an ideal conduit for positioning an endovascular prosthesis to act on the mitral annulus and thereby reshape it.
Examples of minimally invasive apparatus for heart valve repair can be found in U.S. Pat. No. 6,210,432 to Solem, et al., U.S. Pat. No. 7,192,442 to Solem, et. al., U.S. Pat. No. 7,090,695 to Solem, et. al., U.S. Pat. No. 7,192,443 to Solem, et. al., U.S. Pat. No. 6,997,951 to Solem, et. al., U.S. Ser. No. 10/714,462 to Solem, et. al. filed on Nov. 13, 2003 and U.S. Ser. No. 60/530,352 to Solem, et al. filed on Dec. 16, 2003 (the '352 application) all of which are incorporated herein by reference.
One specific example of a minimally invasive apparatus for heart valve repair, as described in greater detail in the '352 application, and as shown in FIGS. 10 and 11 herein, includes an elongate body 410 having a proximal anchor 412 and a distal anchor 414 connected by a bridge 416. The proximal and distal anchors 412, 414 are both stents made from nitinol and both anchors have a mesh configuration including loops 54 of zigzag shaped material having alternating peaks 42. The loops 54 are connected at each peak 42 to form rings 56 of four-sided openings. Both the proximal anchor 412 and the distal anchor 414 are transferable between a compressed state, in which the anchors have a diameter that is less than the diameter of the coronary sinus, and an expanded state, in which the anchors have a diameter that is about equal to or greater than the diameter of the coronary sinus.
As shown in FIG. 10, the bridge 416 is connected between the proximal anchor 412 and the distal anchor 414 by links 418, 419. As shown in more detail in FIG. 11, the link 419 has a base 421 and arms 422 that extend from the base and which are connected to the anchor 414. The link also includes a hole 428 which serves as a means through which resorbable thread 420 may be secured to the bridge.
The bridge 416 is made from a shape memory material and is flexible to allow the body 410 to conform to the shape of the coronary sinus. The bridge 416 includes connected X-shaped elements 424 having a space 425 between adjacent elements. The bridge has two states, an activated state in which the bridge 416 has a first length and a non-activated state, in which the bridge has a second length, the second length being longer than the first length. Resorbable thread 420 which acts as a temporary spacer is woven into the spaces 425 to hold the bridge in its longer non-activated state.
The body is inserted into the coronary sinus of a patient with both anchors 412, 414, in the compressed state and the bridge 416 including resorbable thread 420 in the longer non-activated state. After the anchors 412, 414 are placed in a desired location, they are transformed into their expanded state in which they serve to attach the body 410 to the coronary sinus. After a period of time, during which the wall of the coronary sinus grows around the anchors 412, 414, the resorbable thread dissolves and the bridge 416 transforms from its longer non-activated state to its shorter activated state. The shortening of the bridge 416 draws the proximal anchor 412 and the distal anchor 414 closer together, cinching the coronary sinus and reducing its circumference. This reduction of the circumference of the coronary sinus closes the gap causing mitral regurgitation.
Valve annulus reshaping devices, including those described above, may be manufactured such that they can vary in certain dimensions or characteristics. For instance, the devices may be manufactured so that they foreshorten or otherwise change shape by a specific amount depending on how much reshaping of a valve is necessary. In other words, a physician may have a choice between using a reshaping device that severely remodels an annulus, one that only slightly remodels an annulus, or one that is custom designed to remodel an annulus by a specific amount. Additionally, the valve reshaping devices may also be manufactured to have different lengths and/or anchor sizes. Due to varying degrees of the severity of mitral and tricuspid valve leaflet coaptation as well as varying sizes and lengths of heart valve annuli, it would be advantageous for a physician to know how much reshaping of the valve annulus is necessary as well as having an idea of the size and length of the annulus before inserting the valve reshaping device. This knowledge would allow the physician to choose a device that could reshape the valve annulus by an appropriate amount. Thus, there is a need for a device that a physician may use to gauge the amount of reshaping necessary in a heart valve annulus and/or the size and length of the annulus. Such a device would allow the physician to select an annulus reshaping device to insert into a patient that more closely approximates the amount of reshaping necessary for that specific patient as well as a device that may be custom designed to fit the size and length of the patient's annulus.